Liquefied gas handling system



May 7; 1946.

D. G. ARNDT ETAL LIQUEFIED GAS HANDLING SYSTEM I Filed March 18, 1944 2 Sheets-Sheet l lnvenTors'. Donaldfi. Arndr Samuel K. Holf May 7, 1946.

LI QUEFIY ED GAS HANDLING, SYSTEM D. G. ARNDT ET AL Filed March 18, 1944 2 Sheets-Sheet 2 lnvznfors'. D c mald 6. Arndh Samuel K. Holt Patented May 7,1946

s "PATIENT OFFICE 2.400.037 LIQUEFIED GAS HANDLING SYSTEM Donald G. Arndt, San Bruno, and Samuel K. Holt,

Sacramento, Calif., assignors to Shell Development Company, SanFrancisco, Calif., a corporation of Delaware Application'March 18, 1944, Serial No. 527,381

7 Claims.

The present invention relates to a system for supplying liquefied gas from a storage container to a second containerand more particularly to a system for supplying liquefied petroleum gas from a service truck to small domestic supply tanks.

. In those localities where natural and/or manufactured gas is not available for domestic heating or other purposes, it has become common practice to utilize liquefied petroleum gases stored in small pressure containers, vapor from the top of the container being supplied under pressure to conduits leading to various heating apparatus. The capacityof the domestic containers generally employed is sufficient for approximately 2 months or more supply under average conditions. At the end of this period it is necessary to either refill the domestic container in place or replace it with a container which has been refilled at a depot by the distributor. Since the handling and transportation of these small cylinders under such condition is, under certain conditions, both an expensive and ineflicient procedure, various arrangement have been devised to permit refilling of the cylinders in place from a supply tank carried on a truck. However, as the domestic tank is filled from the supply tank, the pressure in the domestic tank rapidly increases to a point whereat it equals or exceeds the pressure in the supply tank, thus preventing further flow to the domestic tank. In order to overcome this difficulty, it' has become common practice to employ a pressure pump mounted on the service truck in order to fill the domestic tank to its rated capacity. Pressure pumps adapted to handle liquefied gases'are in many instances, however, complicated and expensive and require constant maintenance.

It is an object of th present invention to provide an arrangement whereby transfer of liquefied gas from a supply tank to a second tank may be made without the use of pumping equipment. A further object is to provide such an arrangement which is particularly adapted for servicing ing heat generated by an internal combustion engine to vaporize a portion of the liquefied gas in a container and return the vapors to the vapor tion, will become apparent from the following detailed description thereof, taken together with the accompanying drawings forming a part of the specification and wherein Fig. I is a schematic view showing the general arrangement of the invention;

2 for various products, is also provided with a pressure tank 3 containing liquefied petroleum gas, such as, for example, propane, butane, isobutane or various mixtures of the same. A heat exchanger I, which isidescribed in detail below,

is in flow communication with an intake conduit 8 including valve- Ill leading from the hot water outlet 50 of the truck engine cooling system and upon which tank I may be placed.

In Figs. II and III, pressure tank 3 is supported by cradle 22 which is in turn supported on skids II and I! by means of a plurality of steel leg plates as at I, II, l8, l9 and II (20 and 2| of Fig. IV). Heat exchanger 1 is positioned beneath tank 3 and is supported by conduits 23 and 25.

' Hot water conduit 8 leading to heat exchanger space above. the liquid level in the container.

Other objects, together with some of the advantages to be derived in utilizing the preent invencoil Ill and return conduit 9 both pass through the end wall of heat exchanger I as shown. Vapor conduits 23 and 25 pass from the top of heat exchanger 1 through the center of-tank l and terminate 'at a point near the top of tank 3 in the interior thereof. A second pair of conduits 24 and It are provided around conduits 23 and 25 respectively, being welded to the same at the top end thereof and welded to tank 3 at the bottom thereof, thus providing an air space open to the atmosphere between the inner and outer conduits. A-well fl is provided in the bottom of tank 3 at or near the center thereof. ,Arcuate conduit 21 is in flow communication with well II and the interior of heat exchanger 1.- Channel iron cross elevation through v member fill serves as a guard for arcuate conduit Conduit 52 extends to a point near the bottom of tank 3 and passes out an end wall of tank 3 through a threaded reducing connection at 33. The external extension of conduit 32 leads to valve to which is in turn in how communication with conduit 35 and threaded connection element 35. Conduit it including pressure gauge 38 is in fiow communication with the interior of tank is and pressure relief valve 38 provided with spring it normally urging valve eiement ll to a closed position. Conduit (it leads from pressure relief valve 39 to a diaphragm actuated valve is in conduit ii. Valve actuating rod 68 is normally urged I upwardly against diaphragm M by means oi spring i=2, valve libeing open under these con ditlons. Conduit lt leads to a. pressure chamber in which diaphragm il is disposed. I

A conventional measuring rod for liquefied p..- troleum gases is provided at 29 in order to determine the quantity of material within tank 3. Tank 33 is also equipped with customary safety devices such as a pressure relief valve 58 and fusible plugs at at and ii I.

The unit operates as follows: liquefied gas passes into the bottom of heat exchanger 6 through conduit 21 from tank 3 and finds its own level in conduits 23 and 25. Hot water passing through conduits t and 9 vaporizes the part of the liquefied petroleum gas in heat exchanger 7, the vapors passing through conduits 23 and iii to the vapor space above the liquid level in tank 3. The increased pressure in tank 3 forces liquefied petroleum gas out of tank 8 through conduit 32, valve 3 and conduit 35, which is connected to conduit t (Fig. 1) leading to the container which it is desired to fill. Conduit 32 is utilized additionally to refill pressure tank 3.

In the event that the pressure in tank 3 ex= ceeds the desired maximum, pressure relief valve 39, which has been previously set to operate at this maximum, opens and permits vapor under pressure to enter the pressure chamber above diaphragm M, depressing the diapln'agm and forcing rod 43 downwardly to close valve M. When using propane, for example, it has been found desirable to set pressure relief valve 39 to open at approximately 240 p. s. 1.. -With valve 44 closed, flow of hot water to heat exchanger l is prevented, thus avoiding any further increase in pressure in tank 3. When the pressure in tank 3 drops below the predetermined maximum, spring 6 acts to close pressure relief valve 39. A small orifice 45 is provided in conduit 40, thus permitting vapor trapped in conduit 40 and the pres= sure chamber above diaphragm 4| to escape slowly. As soon as pressure relief valve 39 closes, the pressure above diaphragm 89 will begin to drop as a result of vapor leak through orifice 45 and when the pressure approaches atmospheric, sprin 42 will operate to raise rod 43 and thus open valve ll. 1

The supply of heat to heat exchanger I may also be controlled manually through. valve It zvhkgi is accessible to the operator of the service ruc A particular advantage of the servicing system described above has in the fact that a pressure increase in tank 3 sumcient to overcome the static pressure in the customer's supply tank may be rapidly attained by heating only a small portion of the material from tank 3. In handling pro pane, for example, it has been found that the desired pressure in tank 3 is attained alter supaeoaosv plying hot water to heat exchanger i for a period of time of the order of ten minutes. This is an important factor in equipment of the type described, both from the standpoint of the short period of time required to develop the desired delivery pressure and because heating of the com tents of the delivery tank is avoided. Any system which requires substantial heating of the entire contents of the supply tank in order to increase the pressure therein for deliveries, is inherently inefiicient and undesirable for use in transfer operations of this type, When heated material is supplied to the customer's tank from the delivery tank, the pressure in the customers tank rapidly increases to that of the delivery tank, thus preventing further flow of material to the customer's tank. The present arrangement overcomes these difflculties entirely, material being delivered to the customer's tank from the bottom of supply tank 3 at atmospheric temperatures and the desired pressure increase in supply tank 3 being attained without substantial heating of the contents thereof. The relatively small amount of iquified gas which is contained in heat exchanger 7 is rapidly vaporized and the vapors passing through insulated conduits 23 and 25 immediately increase the pressure of the liquid contained in supply tank 3 without substantial heat exchange with the liquid content of tank 3.

Certain variations and modifications of the arrangement as shown which may be made without departing from the disclosed principles of operation and design, will be apparent to those skilled in the art. For example, the heat supply to heat exchanger 1 may be in the form of hot exhaust gases from the truck engine, or electrical heat energy may be supplied to immersion heaters disposed in the heat exchanger with the truck engine generator as a source of supply, or if necessary or desired for any reason, an independent source of heat energy may be provided. For most purposes and in consideration of the safety factors which must be considered in such equipment it is preferred to employ the arrangement disclosed, 1. e. hot water from the engine cooling system as a source of heat energy for the heat exchanger.

Although conduits 23 and 25 are shown as being insulated from the contents of tank 3 by means of an air space and a. second pair of conduits, the air space being open to the atmosphere, it will be appreciated that other means for insulating the vapor conduits may be employed. For example, a double walled conduit system as shown may be advantageously utilized and the space between each pair of conduits packed with a heat insulatingmaterial such as asbestos, rock wool, glass fiber, etc. Also, the space between each pair of conduits may be sealed at the bottom thereof and the air pumped out to provide vacuum insulation. Alternatively, single walled vapor conduits having a relatively great wall thickness and formed of a heat insulating material such as pressed'asbestos and the like may be employed. In such instances it will be necessary to provide a pressure seal at the bottom of tank 3 at the point where the vapor conduits pass through the tank wall.

The invention claimed is:

1. In liquefied gas dispensing equipment of the class described, the combination comprising a pressure tight supply tank for liquefied-gas, vaporizing means, flow communication means extending from said supply tank below th liquid level therein to said vaporizing means, flow communication means extending from said vaporizing from said supply tank below the liquid level therein to said heat exchanger conduit means extending from said heat exchanger through said supply tank and terminatingat a point above the liquid level in said supply tank, conduit means having a larger diameter and disposed concentric with said first named conduit means extending from the bottom of said supply tank and loined to said first named conduit means at the upper end thereof, said second named conduit means defining an annular insulating space open to'the atmosphere between said first, and second named conduit means, means for supplyingheat to said heat ex- 1 changer and means for withdrawing liquefied gas from said supply tank.

3. In liquefied gas dispensing equipment of the class described, the combination comprising a 5. In liquefied gas dispensing equipment of the class described, the combination comprising a pressure tight supply tank for liquefied gas, a heat exchanger, means for supplying heat to said heat exchanger, gravity flow communication means extending from said supply tank below the liquid level thereof to said heat exchanger, va pair of thermally insulated conduits extending in flow communication with saidsupply tank and with said heat exchanger through said supply tank nearopposite ends thereof andterminating at points above the liquid level in said supply tank, said gravity flow communication means being disposed between said pair of thermally insulated pressure tight supply tank for liquefied gas, a heat exchanger disposed beneath said supply tank, a well in the bottom of said supply tank, conduit means extending in flow communication from said well to said heat exchanger, conduit means extending in flow communication from said heat exchanger through said supply tank and termihating at a point above the liquid level in said supply tank, conduit means having a larger diameter and disposed concentric with said first named conduit means extending from the bottom of said supply tank and-joined to said first named conduit means at the upper end thereof, said second named conduit means defining an annular insulating space'open to the atmosphere between said first and second named conduit means, means for supplying heat to said heat exchanger and de livery conduit means extending from a point within said supply tank below the liquid level therein to a point external to said supply tank.

conduits and means for withdrawing liquefied gas from said supply tank.

6. In liquefied gas dispensing equipment of the class described, the combination comprising a service truck including a liquid cooled internal combustion engine, a pressure tight supply tank for liquefied gas mounted on said service truck, a heat exchanger disposed beneath said supply tank, conduit means ca'rrying hot liquid coolant from said internal combustion engine to said heat exchanger, conduit means returning liquid coolant from said heat exchanger to said internal combustion engine, gravity flow communication means extending from said supply tank below the liquid level therein to said heat exchangenthermally insulated new communication means extending from said heat exchanger through said supply tank and terminating within said supply tank at a point above the liquid level therein and conduit means for withdrawing liquefied gas from said supply tank.

7. In liquefied gas dispensing equipment of the class described, the combination comprising a exchanger, a valve including an actuating element 5 in said conduit means, pressure response means 4. In liquefied gas dispensing equipment of the class described, the combination comprising a pressure tight supply tank for liquefied gas, a heat exchanger, gravity flow communication means 5 means returning liquid coolant from said heat exextending from said supply tank below the liquid level therein to said heat exchanger, thermally.

insulated flow communication means extending from said heat exchanger through said supply tankand terminating at a point above the liquid level therein, conduit means for withdrawing. liquefied gas from said supply tank, conduit means leading in fiow communication from a source of heated fluid to said heat exchanger, a valve including an actuating element in said last named conduit means and pressure responsive means adapted to actuate said actuating element to'close said valve when the pressure in said supply tank 1 reaches a predetermined maximum.

in fiow communication with said simply tank adapted to actuate said actuating element to close 1 said valve when the pressure in saidsupply tank reaches a predetermined maximum, conduit changer to said internal combustion engine, a well I in the bottom of said supply tank, gravity flow communication means between said well and said heat exchanger, a pair of thermally insulated con- 55 duits extending in fiow communication with said supply tank being disposed between said pair or thermally insulamd conduits and means 101- withsupply tank and said heat exchanger through aid supply tank near opposite ends thereof and terminating at points above the liquid level in said 1 91 7 tank, said well in the bottom of said I drawing liquefied gas from said simply tank.

00mm a. lumn'r.

SAMUEL K. HOLT. 

